The advantages of cultivating microorganisms first on a liquid, and subsequently on a solid medium have been recognized in the art. Various devices have been proposed, and these may be divided into two basic systems:
a. A one-component system as set out in French Pat. No. 2 381 103 of Institut Pasteur, filed Feb. 18, 1977. This provides a receipient for the simultaneous biological culture on a liquid and a solid medium, where there is provided a container with a liquid medium at the lower part of the container, and with a solid medium in the throat-section of a screw-thread closure member closing the neck portion of the container.
This system has the drawback of restricted visibility of the solid culture medium, and it is possible to use one solid culture medium only. Furthermore, the system is intended for sterilization by autoclaving, and aseptic assembly.
b. A two-component system, where in one container there is provided a liquid culture medium, in a second container a slide-support of a solid culture medium, the incubation being effected in the first stage in the liquid medium; the containers are attached with each other, the solid medium is contacted with the liquid one, and the incubation is continued on the solid medium.
The two-component system has the serious drawback of possible contamination during the phase of opening the first container and attachment of the second one.
Furthermore, the solid medium is stored and transported in a separate container, and is apt to deteriorate by partial drying out. In the two-component system which is commercially available there exists also the problem of fogging of the neck-section after removal from the incubator, which has been reported in literature to cause problems.
The drawbacks of the known twin-culture media systems has been overcome to a large extent by the novel system of the invention, which has considerable advantages over the existing ones. By making use of special culture media which can be sterilized by gamma-radiation, the necessity of autoclaving is also obviated, resulting in an optimum culture system.